E30 M40 Idle problem

[El_Fishe]

Hi guys, this may or may not have been addressed before but, i've got a really really niggly problem with the motor, It's begun to idle really low, talking around 5 or 6 hundred revs. It occasionally cuts out too when coming up to junctions and lights with the clutch down etc. Sometimes its fine but on other days its a 'mare. Any ideas what it could be?

Thanks in advance

[stitch-626]

i had this problem with the wifes touring, try giving the airfolw meter a clean or replacing it a few quid off here.
finaly welcome to the zone mate.

[El_Fishe]

cheers mate, ill give it a bash in a couple of days, its really pissing me off so i might just give it a bash with a hammer or something, maybe knock some of the shit of it, one more question though, is there a way to get into the afm without removing it or will i have to take it off and dismantle it to give it a clean.

cheers for the welcome dude! lol

[jcjdavis1]

Hi and welcome need to get some pics.up

[bigdek]

i have a 1.8 m40 airflow meter here m8.

Known to be good and i'm 10 mins from you


If you need one

[El_Fishe]

Na think i should be alright just now, thanks much for the offer tho, had the afm off, cleaned everything and its still running shitty, next thing it would seem would be the idle control valve??? any ideas??

Where abouts are you??

[Brianmoooore]

Check out the TPS idle switch, and the convoluted rubber air hose for splits and leaks. (You have to take this hose off to get at the TPS anyway.)

[smithy318i]

After disassembling my engine to replace the FPR, mine has gone the same as yours. Currently running at 500-600 rpm @ idle.

Stalls at the drop of a hat especialy when cold.

TPS was, and still is in perfect working order.
F'ing engine!

[louis2035]

i have a similar problem. my fuel pump sounds really loud and sounds like it is struggling to keep a constant flow as the noise coming from it increases and drecreases with the idle.

[Brianmoooore]

i have a similar problem. my fuel pump sounds really loud and sounds like it is struggling to keep a constant flow as the noise coming from it increases and drecreases with the idle.

What age/model of car?

[louis2035]

car is 325i sport 1991

[El_Fishe]

Just so i make sure im muckin about with the right part, is the tps idle switch right at the base of the windscreen in the middle? with a hose or two running out of the bottom of it?

[Brianmoooore]

car is 325i sport 1991

Was thinking it might have been an early car with two fuel pumps.

[Brianmoooore]

Just so i make sure im muckin about with the right part, is the tps idle switch right at the base of the windscreen in the middle? with a hose or two running out of the bottom of it?

If this is an M40, I think you've found the ICV.
TPS is at the bottom end of the throttle butterfly spindle, and has an electrical plug fitted into it.

[louis2035]

Do you think the fuel pump might be the problem? or would it be worth replacing the fuel filter and adjusting the icv?

[Brianmoooore]

If the fuel pump can keep up with hard acceleration then it must be producing enough flow and pressure. Same goes for the filter. Fuel pump should only just be audible though.
Nothing to adjust on the ICV. Can be cleaned out with carb cleaner, but it's entirely controlled by the ECU.
Always worth checking the operation of the TPS though.

[louis2035]

how do i go about checking the TPS, and what is it? sorry not clued up on all the abbreviations

[Gortour]

Mine has low rough tickover too. Is yours like mine El-Fishe, runs beautifully, goes well, just doesn't like idleing?
Mine seems worse if under load too - by which I mean heater fan, headlights, heated window etc.

[El_Fishe]

Mine has low rough tickover too. Is yours like mine El-Fishe, runs beautifully, goes well, just doesn't like idleing?
Mine seems worse if under load too - by which I mean heater fan, headlights, heated window etc.

Exactly the same, if i switch everything off, lights, stereo, etc etc it idles low, but still idles, if i don't indicate at a junction it 7 or 8 times out of 10 doesnt cut out. Possibly an electrical fault if cleaning the icv doesnt work?

[Gortour]

Mine's not cutting out, just very lumpy at idle... Lumpier with electrics on...
I'm going to check the battery volts at the weekend, all off, and at tickover and with a few revs on. As current drain seems to be an issue, it's possible the alternator or battery are dying. Hasn't failed to turn over yet though.

[Brianmoooore]

how do i go about checking the TPS,

Use the forum search function, it's been covered loads of times.
TPS = throttle position switch
ICV = idle control valve
AFM = air flow meter
FPR = fuel pressure regulator

[louis2035]

MIne is very similar problem to yours gortour and el-fishe. cuts out sometimes when the clutch is in, last night it cut out pulling away from a junction and didnt stat for a few minutes. when trying to start it nothing happened no battery or oil lights came up and the starter motor didnt engage. will check the battery and alternator.

[El_Fishe]

Fixed it...

Pulled out the plug from what i think was the icv at the base of the windscreen and then started the car, idled and drove like a dream, parked up again, put the plug back in, it died first time. So once again i pulled the plug started the car, turned it off, put the plug back in, started the car, and its been fine for the past week.

Can only think that it may have either reset something or there was dirty contacts on the plug, i'll never know, but ive got a cheesy the width of my face at the moment.

[Gortour]

Well done El_Fische. Pleased for you.
Looked at mine again this weekend, Had 11.9v at the battery, started it, no higher. Revved it, and it dropped back to tickover with 14v acros the battery. So maybe just a tickover problem I thought.
I started the car, turned the tickover screw up, turned it off, started it again, and the tickover dropped even lower.
Turned tickover up further, revs went through the roof when I turned the engine off and started it again. Turned it down a bit and tried again, it's been great ever since. Revs to about 1200-1300 on starting cold, then settles slightly. Ticks over at about 750 in gear, 1100 in neutral. (auto box by the way..)
When warm, it ticks over at 850 in neutral and still 750 in gear. Smooth tickover too.

[Brianmoooore]

turned the tickover screw up.

THERE ISN'T ONE!!!!!

[smithy318i]

turned the tickover screw up.

THERE ISN'T ONE!!!!!

he might be messing about with the screw on the TB.

[Brianmoooore]

turned the tickover screw up.

THERE ISN'T ONE!!!!!

he might be messing about with the screw on the TB.

That's what I mean!!

[Gortour]

turned the tickover screw up.

THERE ISN'T ONE!!!!!

Oooh, well the screw on the throttle body that seems to be the return stop...
If it isn't a tickover / throttle return screw, what have I adjusted then please Brian?

[Brianmoooore]

You've adjusted the throttle butterfly stop, which only has one correct position - where BMW set it at the factory.
Idle speed is controlled entirely by the ECU via the ICV.

[Gortour]

Oh ******!
Did find it doing a few wierd things I must admit. I'll have to look into the ICV properly when I get time, though it's running beautifully now, from just tweeking that slightly.
Won't be far at all from the original place, and I did find the nut on it a bit loose, so maybe it moved and I've by chance got it back where it should be.
I live in hope...
Many thanks for that Brian.

[louis2035]

finally got my car running great, discovered my exhaust manifold gasket had blown out. when i replaaced it though found out one of the studs and broke off so had to get it drilled out by a garage. 5 hours labour they charged me for. but now its going great, no idle and cutting out.

[Gortour]

Can't believe how well mine's running now, having tweeked the wrong screw...
Oh well, must have just been incredibly lucky for once, and undone someone else's attempt to adjust the tickover...